The subject invention is relates to ink jet printing apparatus, and more particularly to an ink jet printing apparatus that achieves print dot resolution that is finer than the resolution of the ink jet printing elements of the ink jet printing apparatus.
An ink jet printer forms a printed image by printing a pattern of individual dots at particular locations of an array defined for the printing medium. The locations are conveniently visualized as being small dots in a rectilinear array. The locations are sometimes called "dot locations," "dot positions," or "pixels". Thus, the printing operation can be viewed as the filling of a pattern of dot locations with dots of ink.
Ink jet printers print dots by ejecting very small drops of ink onto the print medium, and typically include a movable carriage that supports one or more printheads each having ink ejecting nozzles. The carriage traverses over the surface of the print medium, and the nozzles are controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to the pattern of pixels of the image being printed.
An ink jet printhead includes an array of nozzles through which droplets of ink are fired. Typically, the distance along the media axis between adjacent nozzles, which is also called the nozzle pitch, is equal to the resolution dot pitch of the desired dot resolution (e.g., 1/600 inch for 600 dpi).
The quality of the printed images produced by an ink jet printer depends to a large degree on the resolution of the printer. Higher or finer resolution wherein the printed dots are more closely spaced produces provides for higher quality images. Higher or finer resolution can be achieved by decreasing the nozzle pitch; i.e., by increasing the nozzle density of the nozzle array. However, as the nozzle spacing becomes finer, the manufacture of nozzle arrays becomes more difficult and the operation of the nozzle arrays becomes less reliable.